While sitting at a red light as she exited The Summit, an upscale shopping center in Birmingham, around midday on Saturday, Briana DiGiorgio watched as a man got out of his car and approached another man dressed in rags and holding a tattered cardboard sign. When she realized what was going on, Briana, a passenger in her best friend's car, started filming with her smartphone.

Witnessed this man giving a homeless man the shirt off of his back, literally. Y’all, it is freezing cold in Alabama. This poor man was standing at a red light desperately trying to stay warm. If you listen closely, you’ll hear the guy proceeding to tell him that he was going to get him something to eat and that he’d be right back. I was in tears. This is the kind of people we need more of in this world. This is absolutely beautiful... #FaithInHumanity

The apparently homeless man had "minimal clothing on," she said, even though the temperature was struggling to reach a high of 31 degrees that day. He had a sweatshirt wrapped around his neck like a scarf.

The other man, wearing a navy down jacket, jeans and a baseball cap, started talking to him and, to the astonishment of Briana and her friend, removed his jacket and put it on the homeless man, who embraced him.

"I thought, 'I have to get it on video, I have to,'" Briana said. "It's something I don't see every day. I posted it so others could witness what I saw."

Briana is heard in the video whispering, "Oh, this is so sweet."

As he leaves, the man who gave up his coat says, "Zip it up and stay warm. I'm going to go get you some food. I'll be right back, okay?"

The video has been viewed from Briana's Facebook page more than 690,000 times since Saturday. It didn't take long for the good Samaritan to be identified as Dr. Rees Oliver, a Birmingham-area neonatologist.

Though Briana hasn't talked to him, she knows he has "a heart of gold," she said. "He should know he's well appreciated."

The most frequently repeated sentiment among those who've commented on the video: "May God bless them both!"

Witnessing the act of kindness, and seeing how many people it has touched, has impacted Briana, too. "It gives you a huge renewed faith in humanity," she said.